The bag is a good size for the rack on my bike. It attaches with two Velcro straps that wrap around the rack and it seems secure enough. It has lots of room inside and two zippered pockets on the outside. All the zippers appear to be waterproof. They're a little bit difficult to zip, but that's to be expected for waterproof zippers. The bag appears to be large enough inside for a six pack of cans of your favorite beverage and some ice to keep it cold. ?